This invention relates to mounts for magnetic transducing heads, and particularly to mounts that are adjustable to change the angle of orientation (e.g., azimuth) of the head with respect to the machine.
In the magnetic transducing art including that of moving discs, drums and tapes it has always been important to maintain a predetermined orientation of the transducing head with respect to the machine and to the recording surface. Orientations in three orthogonal directions are important: first, the head gap must be not "tilted", i.e., it must be in a plane parallel (tangent) to the recording surface at the gap; second the head should squarely face the recording surface; and third, the "azumith" must be strictly transverse to the direction of movement of the recording surface across the gap. The azimuthal orientation is most sensitive and is more easily disturbed than the others; and azimuth field adjustability is therefore of advantage, to ensure interchangeability of records from machine to machine, and even replayability of the same record from time to time on the same machine.
In the art, two systems, and combinations of the two, have been most often used to achieve orientation adjustability. The first system, represented most clearly by U.S. Pat. No. 2,897,288, July 28, 1959 to Wijchman, comprises a mounting plate that is retained in spaced relation to a base by means of three triangularly-spaced bolts that pass freely through the plate and are threaded into the base. The plate is urged away from the base by spring means as that orientation of a head mounted on the plate is usually snugly sensitive to the positions of the three bolts. Selective turning of the bolts can then adjust the tilt and azimuth orientations of the head. However, outside forces accelerations, shocks, and vibrations can always cause transient compression of the springs, so that orientation is temporarily destroyed.
The second system of the art is represented most clearly by U.S. Pat. No. 3,882,543, May 6, 1975 to Richards. In this patent, a head, which is rotatably adjustable in the azimuthal plane, is secured in azimuthal position by two set screws engaging the sides of the head so as to produce oppositely directed moments of rotation. By backing-off one of the screws and tightening the other, the azimuthal position can be changed.
This arrangement overcomes the disadvantages of the first in environments in which the machine is subject to shock or vibration, but has the complication that two screws must be operated to make an adjustment.
A further problem with both systems of the prior art is that the sensitivity or "resolution" of adjustment is a function of the pitch of the adjusting screw; e.g., if the pitch is, say, 40 threads per inch, then for each revolution of the screw, the translation of the head mounting is 0.025 inches. It would be of advantage in some precision uses, if the transition per revolution were very much smaller.
Accordingly, it is an object of the present invention to provide a head mount of adjustable orientation, in which there is substantially no lost-motion play, and in which only one element needs to be generated to perform an adjustment.
It is a further object of the present invention to provide a head mount as above described, having increased sensitivity and precision response to operation of the adjusting element.
It is a still further object of the present invention to provide a head mount as above described, comprising fewer parts and being manufacturable with increased ease and economy.